1. Field of the Invention
The present invention relates to an NTSC/HDTV community receiving system for receiving NTSC and HDTV signals in common.
2. Description of the Prior Art
A high definition television (HDTV) system is now in the midst of development as a future-oriented television broadcasting system. By way of preparation for the practical use of the future HDTV system according to such a trend, a NTSC/HDTV community receiving system which is capable of receiving an HDTV signal as well as the present NTSC signal has been required by countries such as Korea, United States, now employing a NTSC system.
The NTSC/HDTV community receiving system may be made in various manners. In accordance with the present invention, the NTSC/HDTV community receiving system is made of common components of HDTV and NTSC receiving systems.
Referring to FIG. 1, a schematic block diagram of a conventional HDTV receiving system is shown. As shown in this drawing, the conventional HDTV receiving system includes an antenna 200 for receiving an HDTV signal, an HDTV tuner 210 for tuning the HDTV signal from the antenna 200 to a channel required by the user, an HDTV intermediate frequency detector 220 for detecting an HDTV intermediate frequency signal from the tuned HDTV signal from the HDTV tuner 210, an analog/digital (A/D) converter 230 for converting the HDTV intermediate frequency signal from the HDTV intermediate frequency detector 220 into a digital signal, a filter 240 for removing a NTSC interference signal from the resultant digital HDTV signal from the A/D converter 230, and a channel equalizer 250 for compensating for a linear channel distortion of the resultant HDTV signal from the filter 240.
The conventional HDTV receiving system also includes an error corrector 260 for comparing the resultant HDTV signal from the channel equalizer 250 with a pre-stored reference HDTV signal and correcting an error of the HDTV signal from the channel equalizer 250 in accordance with the compared result, a decoder 270 for decoding the resultant HDTV signal from the error corrector 260 to extract original HDTVI and HDTVQ color signals and an original HDTV luminance signal from the HDTV signal of the error corrector 260 which is under a compressed state, and a display processing unit 280 for processing the original HDTVI and HDTVQ color signals and the original HDTV luminance signal from the decoder 270 in a de-gamma manner to display HDTV red (R), green (G) and blue (B) signals.
The operation of the conventional HDTV receiving system with the above-mentioned construction will hereinafter be described briefly.
Upon receiving the HDTV signal of high frequency through the antenna 200, the HDTV tuner 210 tunes the HDTV signal from the antenna 200 to the channel required by the user. The HDTV intermediate frequency detector 220 detects the HDTV intermediate frequency signal of about 6 MHz from the tuned HDTV signal from the HDTV tuner 210.
The HDTV intermediate frequency signal detected by the HDTV intermediate frequency detector 220 is a composite video signal containing luminance and color signals therein, and is processed at a predetermined sampling rate in the A/D converter 230 for its conversion into the digital signal.
The NTSC interference signal is removed from the resultant digital HDTV signal from the A/D converter 230 by the filter 240. The channel equalizer 250 compensates for the linear channel distortion of the resultant HDTV signal from the filter 240 and the error corrector 260 performs the error correction of the resultant HDTV signal from the channel equalizer 250 on the basis of the pre-stored reference HDTV signal.
The decoder 270 extracts the original HDTV signal or the HDTVI and HDTVQ color signals and the HDTV luminance signal from the resultant HDTV signal of the error corrector 260 which is under the compressed state, by decoding the HDTV signal from the error corrector 260. The display processing unit 280 displays the HDTV R, G and B signals by processing the original HDTVI and HDTVQ color signals and the original HDTV luminance signal from the decoder 270 in the de-gamma manner.
Noticeably, the HDTV receiving system described herein with reference to FIG. 1 is nothing but an example of various HDTV receiving systems. However, all the various HDTV receiving systems operate to receive the HDTV signal, but all have the disadvantage that they cannot receive the presently used NTSC, PAL and SECAM signals commonly with the HDTV signal.